This invention relates to sensing small amounts of selected materials, and, more particularly, to the application of optical absorption spectroscopy to sensing small amounts of materials. This invention was made with government support under Contract No. W-7405-ENG-36 awarded by the U.S. Department of Energy. The government has certain rights in the invention.
There are many applications for the detection of trace quantities of materials in solutions. For example, ultrasensitive analysis requirements exist in forensic applications, intelligence gathering, and biomedical analysis. Artificial nanoparticles may be used as tracers in environmental research or as labels for chemical analysis. Large labeled molecules are used in DNA identification, protein identification, and tracking man-made polymers. In addition, quality control applications particularly include material purity determinations in the semiconductor industry, pharmaceuticals, and in refrigerant chemicals.
There are sensitive detection techniques available, but each has some limitation, i.e., limited sensitivity, limited feature for detection, cost, and the like. Mass spectroscopy is very sensitive to small quantities of materials but it is inherently a gas phase or vacuum-based technique. A complex interface is needed with solid or liquid samples and that interface can introduce losses from the samples. Solution-based samples are output from a number of analytical methods, e.g., electrophoresis and liquid chromatography. It is desirable for an analytical tool to be able to access materials in solution rather than require the sample in a gas phase.
Fluorescence techniques are quite sensitive and can be used on liquid samples. But the technique is limited to only the relatively small number of molecular species that fluoresce with high efficiency. Photothermal and photoacoustic techniques are applicable to liquid samples with an analyte that absorbs light, but the technique is not as sensitive as fluorescence spectroscopy and is not useful in some applications.
The present invention overcomes the above problems and a bubble chamber is adapted for spectroscopic analyses. Accordingly, it is an object of the present invention to provide a highly sensitive analytical technique that is useful with liquid solutions of small quantities of analyte.
Another object of the present invention is to provide a spectroscopic technique that is relatively insensitive to environmental noise.
Yet another object of the present invention is to provide a spectroscopic technique that is useful with a wide variety of analytes.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.